1. Field of the Invention
This invention relates to an aerating unit, more particularly to an aerating unit for treating a body of waste water.
2. Description of the Related Art
Processes for aerobic biotreatment of municipal or industrial waste water or sewage had been well developed. The known processes involve a preliminary treatment which separates floating larger particles, organic solid suspensions, or oil from a body of waste water, an intermediate treatment which includes an aerating unit that provides oxygen to be dissolved in the body of waste water for allowing active sludge to decompose aerobically organic compounds dissolved in the body of waste water, and a final treatment which includes a sedimentation apparatus for precipitating solid particles to separate the treated waste water from the precipitates. The aerating unit is normally designed to provide fine air bubbles dispersed in the body of waste water so as to replenish continually the waste water with dissolved oxygen to enhance the aerobic biotreatment. The retention time and the size of the air bubbles generated by the aerating unit are very important factors to ensure effective dissolution of the oxygen in the waste water.
FIG. 1 illustrates a conventional aerating unit which includes a plurality of disk-shaped diffusers 14 mounted in a container 1 which contains a body of waste water. The diffusers 14 are connected to an air blower 12 via a pipeline 11. Each diffuser 14 is formed with a plurality of small apertures for generating air bubbles dispersed in the body of waste water when the air blower 12 is activated. Since the air bubbles thus formed rise straightly by virtue of buoyancy, the air bubbles generated by each diffuser 14 in the body of waste water are dispersed within a relatively narrow area, and the retention time of the air bubbles is relatively short, thereby necessitating the use of many diffusers 14 in the container 1.
FIG. 2 illustrates another conventional aerating unit which is similar to the above described aerating unit except that an agitating device 26 is mounted in a container 2 above a plurality of diffusers 25. The agitating device 26 pushes waste water downwardly to mix with rising air bubbles generated by the diffusers 25, and provides turbulence in the body of waste water so as to enhance the dispersion of the air bubbles when the agitating device 26 is actuated. While the dispersion of the air bubbles in the body of waste water can be enhanced by utilizing the agitating device 26, the dispersion of the air bubbles in the body of waste water is still unsatisfactory. Moreover, the diffusers 25 are normally spaced apart by a relatively long distance from the bottom of the container 2, thereby decreasing the retention time of the air bubbles.
FIG. 3 illustrates yet another conventional aerating unit 3 which includes a submersible motor 31 immersed in a body of waste water, an air housing 33 connected to the motor 31 and extending downwardly therefrom, an air conduit 34 connected to the air housing 33 and extending upwardly therefrom and through the surface of the waste water, and a diffuser 36 connected to the air housing 33 and extending downwardly therefrom. The diffuser 36 is formed with a plurality of openings 35. The submersible motor 31 has a shaft extending downwardly therefrom into the air housing 33. The shaft is provided with a propeller 32 within the air housing 33 for introducing air into the diffuser 36 from above the surface of the waste water via the air conduit 34 and the air housing 33, and for driving air out of the diffuser 36 to form fine air bubbles dispersed in the body of waste water when the shaft is rotated. The horsepower of the submersible motor 31 must be adequate to overcome a water head from the diffuser 36 to the surface of the waste water in order to suck atmospheric air into the air housing 33 and to drive the air out of the diffuser 36. However, the deeper the location of the aerating unit 3 in the body of waste water, the larger will be the horsepower requirement for the submersible motor 31 to ensure sufficient air flow into the body of waste water.
Therefore, it is an object of the present invention to provide an aerating unit that is capable of overcoming the aforementioned problems commonly associated with the prior arts.
Accordingly, an aerating unit of this invention is adapted to treat a body of waste water and comprises: a container adapted for storing the body of waste water; a submersible motor disposed in the container and having a shaft extending downwardly and outwardly therefrom into the body of waste water, the shaft having a bottom free end provided with a propeller; an air conduit adapted to be connected to an air supply at one end, and extending into the container at the other end which defines an air outlet adjacent to and facing toward the propeller, the air conduit being adapted to introduce air into the body of waste water stored in the container, thereby generating larger air bubbles inside the container that are directed toward the propeller, the motor being operable so as to enable the propeller to break the larger air bubbles into finer air bubbles that are directed downwardly; and a base disposed vertically below and aligned with the motor in the container, the base having a curved surface which is convex in a direction toward the propeller for deflecting the finer air bubbles directed from the propeller in radial directions of the curved surface in the body of waste water.